1. Field of the Invention
This invention relates generally to the control of optical imaging cameras and more particularly to the control of the light levels and sensor-object distance parameters for an electronic camera system.
2. Discussion of the Prior Art
Charge Coupled Device (CCD) imaging cameras are generally well known and can provide a relatively high standard of image resolution. Although not limited to underwater applications, CCD cameras have been found to be particularly useful in connection with an underwater optical system where the optical imagery data is not or cannot be reviewed in real time by a human operator.
The current state of the art for setting optical camera system lighting levels in underwater imaging systems typically uses an instrument that senses the underwater imaging environment called a transmissometer which operates to determine only the volume attenuation coefficient of the water medium. Currently available transmissometers operate to a depth of a few thousand meters; however, such instruments normally require recalibration prior to every underwater mission of twenty four hours or less.
The ability to provide all the necessary information to ensure that quality optical images are being collected without the use of a transmissometer would result in a savings in weight and the expense associated with the development and production would be a significant improvement. The elimination of a housing comprised of titanium or other expensive and heavy material along with the transmissometer would also be a valuable advancement in the art. This would also remove the problem of the electronics stability of the illumination and receiver devices in the transmissometer which cannot be effectively monitored or calibrated during data collection which is needed for accurate image operation monitoring.
Presently lacking is a system and/or method for adaptively adjusting the lighting levels and the camera distance between sensor and object which for an underwater vehicle comprises its altitude above the sea floor. Such a control is particularly desirable for an underwater optical system mounted on an autonomously operated vehicle where real time imagery cannot be reviewed by a human operator. Thus it would be of vital importance if one could control an in-situ CCD electronic camera without the need of a transmissometer or human assistance so that imaging affects of not only the water medium, but also of any changes to the lighting and camera efficiency characteristics can be sensed and changed throughout a data collection mission and thus eliminate the need for real time operator review of the optical imagery and eliminate the need for other sensor hardware.